The invention relates to a circuit arrangement for the electronic level control of a sound signal, comprising an amplifier circuit which is inserted into a sound signal path and the gain of which can be controlled in dependence on a variable direct control voltage, and with a voltage-adjusting stage for generating the variable direct control voltage, from the output of which the variable direct control voltage generated is supplied to the amplifier circuit for controlling its gain.
Such a circuit arrangement is known, for example, from DE-AS 2,136,247. In this known circuit arrangement, the amplifier circuit exhibits a differential amplifier consisting of two bipolar transistors and the voltage-adjusting stage is formed by a variable resistance element which is connected to a direct voltage source and by means of which a direct control voltage is generated which is supplied to the base of a third bipolar transistor of the amplifier circuit, which forms a current source for the two transistors of the differential amplifier and which, in dependence on the direct control voltage supplied to its base, controls the current supplied by it to the two transistors of the differential amplifier and thus the signal coupling between these two transistors. In this known circuit arrangement, the entire range of adjustment of the differential amplifier for controlling the level or adjusting the level, respectively, of a sound signal is achieved by means of relatively small changes of the direct control voltage as a result of which, however, there is a relatively large dependence of the adjustment characteristic of the differential amplifier on tolerances of the components and voltage values and on thermal influences.
Furthermore, relatively high voltages and relatively high currents are required for achieving the most optimum adjustment characteristic of the differential amplifier in this known circuit arrangement. For the case where the known circuit arrangement is used for the level control or level adjustment, respectively, of stereo signals, in which case, as can be seen from DE-AS 2,136,247, such a differential amplifier is then provided in each of the two stereo channels, there is furthermore the problem that due to the aforementioned tolerance- and temperature-dependence, the same adjustment effect for level control or level adjustment, respectively, can only be achieved with great difficulty over the entire adjustment range for both stereo channels.